Are any of the facilities visited as part of the Venice/Florence/Rome trip (i.e., Florence's Accademia Gallery, Vatican Museums and Sistine Chapel, St. Peter's Basilica, etc.) toured after hours or as part of special, private tours? Or are the Rick Steves' tour groups part of the general tourist groups at those sites?
Probably best to ask here:
https://community.ricksteves.com/travel-forum/tours
That said, the RS guides did a decent job of arranging to visit popular sites early, though not "special" times.
On this RS tour, we visited the Accademia in Florence around 5 PM. It wasn't especially crowded. We were at the Vatican Museum about when it opened, it was very crowded but we didn't have to wait in line long. The tour took us into the Sistine Chapel and gave us about half an hour there among the throngs. It took us into St. Peter's via the Vatican, so no waiting for that, and left us there to spend as much time as we wanted.
I found the Vatican so crowded that it interfered seriously with my appreciation of the place, but I wasn't surprised or disappointed because I'd expected big crowds. Our guide did a great job. Time didn't allow a visit to the Raphaels or a lot else. If you want a really uncrowded experience, you might consider some of the early-morning or evening tours offered by others for beaucoup bucks.